True Fakes: Scientists Make Simulated Moondust

Dec.
28 , 2006: Life is tough for a humble grain of dirt
on the surface of the Moon. It's peppered with cosmic rays,
exposed to solar flares, and battered by micrometeorites--shattered,
vaporized and re-condensed countless times over the billions
of years. Adding insult to injury, Earthlings want to strip
it down to oxygen and other elements for "in situ resource
utilization," or ISRU, the process of living off the
land when NASA returns to the Moon in the not-so-distant future.

But,
as Robert Heinlein famously observed, "the Moon is a
harsh mistress." Living with moondust and striping it
down may be trickier than anyone supposes.

Right:
A speck of Moon dirt. The strange shape tells a tale of violence:
It results from the welding of rock, mineral and glass by
the heat of micrometeoroid impacts. Image credit: David S.
McKay, NASA/JSC.

To
find out how tricky, researchers would like to test their
ideas for ISRU and their designs for lunar rovers on real
lunar soil before astronauts return to the Moon. But there's
a problem:

"We
don't have enough real moondust to go around," says Larry
Taylor, director of Planetary Geosciences Institute at the
University of Tennessee in Knoxville. To run all the tests,
"we need to make a well-qualified lunar simulant."
And not just a few bags will do. "We need tons of it,
mainly for working on technologies for diggers and wheels
and machinery on the surface," adds David S. McKay, chief
scientist for astrobiology at the Johnson Space Center (JSC).

Taylor
and McKay are lead members of a small group of self-styled
"lunatics" whose careers have focused on lunar soil
and rocks. They are among several consultants to NASA's Marshall
Space Flight Center (MSFC), which manages the Lunar Regolith
Simulant Development Program.

Carole
McLemore is the program manager at Marshall. Back in the 1990s,
she explains, researchers used a lunar simulant called JSC-1
developed at JSC. But "there is no more JSC-1 available."
So, to get started, researchers at Marshall are working with
the Astromaterials Research and Exploration Science office
at Johnson to create a replica of the JSC-1 simulant: JSC-1A.
It comes in three types based on grain size (fine, medium
and coarse). MSFC has also begun work on more demanding simulants
representing various locations on the Moon.

Until
the Apollo astronauts brought lunar soil samples to Earth
during 1969-72, the belief was that the Moon's dry, airless
environment left the soil largely undisturbed. Reality is
much harsher.

Micrometeorites,
many smaller than a pencil point, constantly rain onto the
surface at up to 100,000 km/hr (about 62,000 mph), chipping
off materials or forming microscopic impact craters. Some
melt the soil and vaporize and re-condense as glassy coats
on other specks of dust. Impacts weld debris into "agglutinates."
Complicated interactions with the solar wind convert iron
in the soil into myriads of "nano-phase" metallic
iron grains just a few nanometers wide.

"Some
of the stuff that got into the Apollo spacecraft was very
finely ground," McKay said. Dust was everywhere and impossible
to brush off. All the lunar astronauts had lung reactions
to this dust, some more than others, like Harrison H. (Jack)
Schmitt's "lunar dust hay fever."

The
Apollo specimens are America's Crown Jewels and are doled
out in ultra-small samples to scientists who can demonstrate
that nothing else will do for high-value experiments. Renewed
interest in lunar exploration in the late 1980s meant that
lunar simulants were needed to test schemes for building structures
on the Moon or for extracting oxygen and other materials.

That
led to JSC-1 in 1993, made of basaltic volcanic cinder cone
deposits from a quarry near Flagstaff, AZ. The 25-ton lot
-- distributed in 50-pound bags -- proved popular.

"We're
totally out, but that's soon to be corrected," said McKay.
MSFC has a Small Business Innovative Research (SBIR) contract
with Orbitec of Madison, WI, to manufacture about 16 metric
tonnes of three types of JSC-1A: 1 tonne of fines (delivered);
14 tonnes of moderate grains (being delivered); and 1 tonne
of coarse grains (coming soon). The U.S. Geological Survey
in Denver and the University of Colorado at Boulder -- key
partners -- are checking the chemical, mineralogical, and
geotechnical properties.

Right:
This photomicrograph of soil from a lunar mare hints at the
underlying variety of genuine Moon dirt and the difficulty
of reproducing it. [Larger
image]

MSFC
is developing three new simulants. Two will represent mare
and polar highlands regions. A third will represent the glassy,
sharp, jagged edges of regolith that test the best of hardware
and humans. But matching every location on the Moon would
require large numbers of small, unique, expensive batches.

"Instead,
we will develop root simulants and manufacture specific simulants
from these, but also enable investigators to enhance the products
as needed," McLemore added. "I liken this process
to baking a cake: depending on the type of cake you want,
you need certain ingredients for it to come out right and
taste right. Getting the recipe right whether for a cake or
lunar simulants is critical."

For
example, the new mare simulant will be enriched with ilmenite,
a crystalline iron-titanium oxide. Source materials used to
produce the three simulants will potentially come from locations
as diverse as Montana, Arizona, Virginia, Florida, Hawaii,
and even some international sites.

Initial
lots will weigh just tens of pounds to ensure that the simulant
is made correctly. "Eventually we will scale up to larger
quantities when we can make sure that there is little variation
from batch to batch," McLemore said.

Once
NASA understands how to make the various simulants, plans
are to farm the work out to companies to produce larger batches.
"We will have certification procedures in place for vendors
to follow so users know that the simulants meet the NASA standards,"
McLemore said.

And
that will be the best way to tell it's a "true fake."
Accept no substitutes.

How
do you know when the fake is true? McLemore
answers: "We use Apollo core samples and other
lunar data to define the figures of merit (FOMs) that
we have generated as a mathematical reference to compare
the 'goodness' of the simulants against known lunar
regolith data." NASA also confers with other groups
who have developed their own simulants, such as Japan's
FJS-1 and MKS-1 and Canada's OB-1.

Dust,
in particular, is a critical simulant need. Mark Hyatt
of Glenn Research Center is working to characterize
dust for development of a simulant by MSFC. Even Martian
soil simulants will need to be developed in time.

"No
matter who made the simulant, unless all simulants'
properties are understood, there is no way to ensure
'apples to apples' comparison of research performed
by scientists and engineers," she cautions. Thus,
even the same tests with the same tools can produce
conflicting results.